Dynamic radio coverage area transition management

ABSTRACT

A coverage transition is performed where a compensation service area is expanded to cover an energy saving service area and the energy saving service area is deactivated. The coverage transition is managed by transferring user equipment devices (UE devices) from an energy saving service area to a transition service area that at least partially overlaps with the energy saving service area. The UE devices may be transferred using a handover procedure between communication stations where each UE device is assigned communication frequencies for communication with the transition communication station that are not used by the energy saving communication station or the compensation service area, thereby avoiding, or at least minimizing, interference. After all UE devices are transferred from the energy saving service area, the communication stations are configured to deactivate the energy saving service area and to expand the compensation service area to cover the energy saving service area.

PRIORITY

The present application claims is a continuation of and claims priorityto U.S. application Ser. No. 14/781,527, entitled “DYNAMIC RADIOCOVERAGE AREA TRANSITION MANAGEMENT” and filed on Sep. 30, 2015, whichis a national stage application of PCT/US2014/033054, entitled “DYNAMICRADIO COVERAGE AREA TRANSITION MANAGEMENT” and filed on Apr. 4, 2014,which claims priority to U.S. Provisional Application No. 61/809,177,entitled “Methods for Controlling Dynamic Radio Coverage AreaTransitions” filed Apr. 5, 2013, and to U.S. Provisional Application No.61/822,203, entitled “Methods for Managing Transitions Between CellCoverage Configurations” filed May 10, 2013, all of which are assignedto the assignee hereof and hereby expressly incorporated by reference intheir entirety.

FIELD

This invention generally relates to wireless communications and moreparticularly to apparatuses, systems, and methods for managing dynamicradio coverage area transitions.

BACKGROUND

Many wireless communication systems employ transceiver stations or radioheads to provide service within geographical service areas, where theboundaries of a service area are determined by the radio coverage of itsassociated transceiver station. Wireless service is provided to userequipment (UE) devices within each service area. These service areas aresometimes referred to as “cells”. Although the term “cell” sometimesrefers to the geographical area where multiple frequencies are used,increasingly the term “cell” is used to refer to the geographicalservice area where a single uplink resource and downlink resource isused to communicate with the UE devices. For example, where TimeDivision Duplex (TDD) is used, a single frequency may be used for uplinkand downlink at different times within the “cell”. Where FrequencyDivision Duplex (FDD) is used, a single uplink/downlink frequency pair(one uplink frequency and one downlink frequency) is used within a“cell”. As discussed herein, one or more frequency resources may be usedin a service area. As a result, a service area may be a cell or maycontain multiple cells. In one common arrangement, each service area isadjacent to several other service areas to provide ubiquitous coverageover a large geographical area. The service areas may overlap slightlybut generally do not provide service within the same geographical area.In many situations, there may be an advantage to dynamically change theconfiguration of the service areas, such as by selectively reducing thesize of some service areas while expanding the size of one or more otherservice areas to provide service within the area previously serviced bythe service areas that were reduced. Such dynamic service areaconfiguration changes may allow for more efficient operation of thesystem. For example, a service area with only a small number of UEdevices may be reduced to zero by deactivating its associatedtransceivers and an adjacent service area that is serving several UEdevices but has available capacity may be expanded to provide radiocoverage for the UE devices previously contained in the reduced servicearea. Therefore, a service area that is reduced may be referred to as anenergy saving service area since the energy consumed by its associatedtransceivers is reduced or eliminated and a service area that is reducedto zero may be referred to as a deactivated service area. A service areathat is expanded in cooperation with a service area that is reduced maybe referred to as a compensation service area. UE devices being servedby an energy saving service area may lose their connection with thenetwork if they are not handed over to another service area before theservice area is deactivated. If the energy saving service area and thecompensation service area operate on the same frequency resources, UEdevices being served by an energy saving service area may lose theirconnection with the network if the compensation service area is expandedbefore the UE devices are handed over to another service area because ofthe interference between the energy saving service area and thecompensation service area. As discussed below, management techniques areneeded to control the dynamic coverage area configuration transitions.

SUMMARY

In a cellular communication system, a coverage area configurationtransition is performed where a compensation communication station isconfigured to expand a compensation geographical service area(compensation service area) to cover an energy saving geographicalservice area (energy saving service area) and an energy savingcommunication station is configured to deactivate the energy savingservice area such that the energy saving communication station does notprovide wireless service within the energy saving service area. Theservice area configuration transition is managed by transferring userequipment devices (UE devices) from an energy saving communicationstation providing wireless service in the energy saving service area toa transition communication station having a transition geographicalservice area (transition service area) that at least partially overlapswith the energy saving geographical service area. The UE devices may betransferred using a handover procedure where each UE device is assignedcommunication frequencies for communication with the transitioncommunication station that are not used by the compensation servicearea, thereby avoiding, or at least minimizing, interference betweenthese UE devices and the compensation service area as it is expanding.After all UE devices are transferred from the energy savingcommunication station, the energy saving communication station isconfigured to deactivate the energy saving geographical service area andthe compensation communication station is configured to expand thecompensation geographical service area to cover the energy savinggeographical service area. For this procedure, the compensationcommunication station and the transition communication station may bethe same, such that UE devices may be transferred to the samecommunication station that provides the compensation service area ifthis communication station operates frequency resources different thanthose used by the compensation service area and the energy savingservice area and that cover the energy saving service area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an illustration of geographical service areas in a cellularcommunication system where coverage area transitions are managed using atransition geographical service area (transition service area).

FIG. 1B is a block diagram of an example where the compensationcommunication station and the transition communication station areformed by two radio heads connected to a single station controller.

FIG. 1C is an illustration of geographical service areas in a cellularcommunication system where the transition communication station, thecompensation communication station, and the energy saving communicationstation are connected through a backhaul.

FIG. 2 is an illustration of a coverage area configuration transitionwhere the energy saving service area is deactivated and the compensationservice area is expanded to provide wireless service within thegeographical region of the energy saving service area.

FIG. 3 includes illustrations of a coverage area transition where thetransition service area covers a plurality of smaller service areas andthe compensation service area is expanded to cover more than one energysaving service area.

FIG. 4 is an illustration of the transition, compensation, and energysaving service areas with neighbor service areas.

FIG. 5 is a message flow diagram between the compensation communicationstation, the energy saving communication station and other communicationstations.

FIG. 6A is an illustration of coverage areas in a cellular communicationsystem where coverage area transitions are managed using a transitionservice area provided by the same communication station that providesthe compensation service area.

FIG. 6B is an illustration of the cellular communication system wherethe compensation station includes a station controller and two radioheads.

FIG. 7 is an illustration of a coverage area configuration transitionwhere the energy saving service area 106 is deactivated and thecompensation service area is expanded to provide wireless service withinthe geographical service area of the energy saving service area.

DETAILED DESCRIPTION

Dynamic coverage area configuration transitions are managed using atransition service area that overlaps with the energy saving servicearea and operates on different frequency resources than the energysaving service area. Prior to expanding the compensation service area,UE devices are transferred from the energy saving communication stationproviding the energy saving service area to the transition communicationstation providing the transition service area which uses differentcommunication resources (frequencies) than used by the energy savingservice area and the compensation service area. After the UE devices aretransferred to the transition communication station, the energy savingcommunication station is configured to deactivate the energy savingservice area and the compensation communication station is configured toexpand the compensation service area to cover the region previouslyserviced by the energy saving communication station in the energy savingservice area. At least some of the UE devices previously receivingservice from the energy saving communication station in the energysaving service area can then be transferred to the compensationcommunication station now providing the expanded compensation servicearea.

In typical implementations, the transition service area is a relativelylarger geographic service area providing wireless service to UE deviceswhere the service area includes adequate capacity to handle the UEdevices transferred from the energy saving service areas. For example,the transition service area may be provided by a macrocell eNB having aservice area at least partially covering the energy saving service. Inanother example, a compensation eNB may provide multiple service areaswhere one service area overlaps with the energy saving service area. Forsuch an arrangement, the compensation eNB may include multiple radioheads where at least one radio head operates wireless signals within thetransition service area at frequencies different from the frequenciesused by the energy saving service area and the compensation servicearea. A transfer of UE devices from the transition service area to thecompensation service area, in this case, includes assigning anuplink/downlink frequency pair used in the compensation service area andmay involve transferring the UE device from the radio head providing thetransition service area to the radio head providing the compensationservice area. A single frequency may be assigned for the uplink anddownlink where TDD is employed.

FIG. 1A is an illustration of geographical service areas in a cellularcommunication system 100 where coverage area configuration transitionsare managed using a transition geographical service area (transitionservice area) 102. Communication stations provide wireless servicewithin a geographical service areas represented by circular areas. Intypical implementations of the cellular communication system 100,several adjacent transition service areas may cover large areas whereeach transition service area includes several smaller service areaspositioned adjacent to each other within the transition service area102. In the interest of brevity and clarity, however, FIG. 1A shows onlytwo smaller cells 104, 106 within a single transition service area 102.The circular shapes representing the service areas generally illustratethe relationships between the areas and do not necessarily depict theactual shapes of the service areas. The coverage area transitionmanagement techniques discussed with reference to FIG. 1A may be appliedto numerous coverage area transition scenarios. For example, severalcommunication stations can be configured to deactivate several energysaving service areas and a compensation communication station can beconfigured to expand the compensation service area to cover the ESgeographical service areas in accordance with the techniques discussedherein. The cells may have any of several shapes and sizes.

As noted above, a transition service area 102 may be formed by anycommunication station providing a service area that has adequateresources to handle UE devices transferred from the energy savingservice area of an energy saving communication station. Although thetransition service area may be a service area dedicated only formanaging coverage area transitions, most implementations include using aservice area providing communication service to UE devices and that hasadequate capacity facilitate the dynamic coverage area transition.

For the example of FIG. 1A, the transition service area 102 covers acompensation geographical service area (compensation service area) 104and an energy saving geographical service area (ES service area) 106. Insome situations, the transition service area 102 may not cover all ofthe compensation service area 104 and/or the ES service area 106. Forthe example, a transition communication station 108 provides wirelessservice in the transition service area 102, a compensation communicationstation 110 provides wireless service in the compensation service area104 and an energy saving communication station (ES communicationstation) 112 provides wireless service within the ES service area 106.Each communication station 108, 110, 112, which also may be referred toas an access node, access point, eNodeB, eNB, base station, and otherterms, includes a transceiver and station controller. The transceiver,or radio head, is typically collocated with the station controlleralthough, in some situations, the station controller may be physicallyseparated from the radio head. The radio head at least includes radiofrequency (RF) transceiver equipment such as antennas, transmitters, andreceivers, for transmitting and receiving wireless signals. Typically,radio heads do not include higher level processing and control functionswhich are performed by the associated station controller. Depending onthe particular implementation, the communication stations of FIG. 1A maybe a standalone communication station with a dedicated stationcontroller or may be formed with a radio head and a station controllerconnected to one or more other radio heads. In one example, thecompensation communication station 110 is also the transitioncommunication station 108 where the compensation communication station108 provides the transition service area 102 using one set offrequencies and provides the compensation service area 104 using anotherset of frequencies. Therefore, the transition communication station 108is illustrated with dashed lines in FIG. 1A to indicate that, in somesituations, the transition communication station 108 may be part of thecompensation communication station 110. As discussed below withreference to FIG. 1B, a single station controller can be connected totwo radio heads to form the transition communication station 108 and thecompensation communication station 110.

As discussed herein, a geographic service area (or service area) is ageographic region where a UE device can adequately communicate with atransceiver providing the wireless service within the geographic region.A geographic service area may use a single uplink/downlink frequencypair or may use multiple frequency pairs or may use different timeperiods to distinguish uplink/downlink signals on the same frequencyresource. For Frequency Division Duplex (FDD), a “cell” is often used todescribe a geographic service area using a particular bandwidth (such as5 MHz) within a single uplink/downlink frequency band pair. Accordingly,the geographic service regions, as discussed herein, may include onecell where only a single frequency pair is used or may include multiplecells where multiple frequency pairs are used. Each geographic servicearea may be provided by one or more radio heads where multiple radioheads may be connected to a single station controller. In somesituations, for example, each radio head provides service using a singlefrequency pair resulting in multiple radio heads providing servicewithin the geographic service area where multiple frequency pairs areused within the service area. For Time Division Duplex (TDD), a cell canbe described as a geographic service area using a particular bandwidthwithin one frequency band and the uplink and downlink signals areassigned different time periods. For TDD systems, geographical serviceareas may include multiple cells. For the discussion herein, acommunication station includes the equipment and code to provide asingle service area. Therefore, a communication station can beconfigured to adjust the size and shape of its service area. This mayinclude adjusting multiple cells or may include adjusting a single cellwhere a service area employs a single communication resource (e.g., asingle uplink/downlink frequency carrier pair).

Since the location, shape, and size of the service is determined atleast in part by wireless transmission and reception with thecommunication station, the service area's location is determined by thelocation and operation of the radio head. Each communication station108, 110, 112 provides wireless communication services to wirelesscommunication user equipment devices (UE devices) 114, 116, 118 withinthe corresponding geographical service area. Several communicationstations are typically interconnected through a backhaul (not shown inFIG. 1A) and to a network controller (not shown in FIG. 1A) to provideseveral service areas to cover large areas. The backhaul may include anycombination of wired, optical, and/or wireless communication channels.For the examples herein, the network controller includes thefunctionality of the Mobility Management Entity (MME) and the PacketGateway (P-GW).

A cellular communication system is typically required to adhere to acommunication standard or specification. The communication specificationdefines at least a data channel and a control channel for uplink anddownlink transmissions and specifies at least some timing and frequencyparameters for physical downlink control channels from a base station toa wireless communication device. The Third-Generation PartnershipProject Long-Term Evolution (3GPP LTE) communication specification is aspecification for systems where communication stations (eNodeBs) provideservice to wireless communication devices (UE devices) using orthogonalfrequency-division multiplexing (OFDM) on the downlink andsingle-carrier frequency-division multiple access (SC-FDMA) on theuplink. Although the techniques described herein may be applied in othertypes of communication systems, the exemplary systems discussed hereinoperate in accordance with a 3GPP LTE communication specification.

Therefore, for the examples herein, the coverage communication station108 includes a wireless transceiver that transmits downlink signals 122to one or more UE devices 114 within the transition service area 102 inaccordance with 3GPP LTE and receives uplink signals 120 from one ormore UE devices 114 within the transition service area 102 in accordancewith 3GPP LTE. The compensation communication station 110 includes awireless transceiver that transmits downlink signals 124 to one or moreUE devices 116 within the compensation service area 104 in accordancewith 3GPP LTE and receives uplink signals 126 from one or more UEdevices 116 within the compensation service area 104. The energy savingcommunication station 112 includes a wireless transceiver that transmitsdownlink signals 130 to one or more UE devices 118 within the energysaving service area 106 in accordance with 3GPP LTE and receives uplinksignals 128 from one or more UE devices 118 within the energy savingservice area 106 in accordance with 3GPP LTE.

The UE devices 114, 116, 118 may be referred to as mobile devices,wireless devices, wireless communication devices, and mobile wirelessdevices, and UEs, as well as by other terms. The wireless communicationdevices include electronics and code for communicating withcommunication stations (eNBs) and, in some cases, with other devicesincluding other UE devices. The UE devices include devices such as cellphones, smart phones, personal digital assistants (PDAs), wireless modemcards, wireless modems, televisions with wireless communicationelectronics, and laptop and desktop computers, as well as other devices.The combination of wireless communication electronics with an electronicdevice, therefore, may form a wireless communication device. Forexample, a wireless communication device may include a wireless modemconnected to an appliance, computer, or television.

Although the compensation service area may slightly overlap the energysaving service area, the two areas in FIG. 1A use the same frequenciesand, therefore, interference may occur where there is significantoverlap of the geographic service areas. A different frequency from thefrequencies used by the two smaller areas, however, is used to provideservice within the transition service area 102. As a result,communication within the transition service area does not interfere withcommunication within the compensation service area or the energy savingservice area.

FIG. 1B is a block diagram of an example where the compensationcommunication station 110 and the transition communication station 108are formed by two radio heads 134, 136 connected to the a single stationcontroller 132. The station controller 132 establishes the transitionservice area 102 by transmitting and receiving signals though the radiohead 134 and establishes the compensation service area 104 bytransmitting and receiving signals through the radio head 136.

FIG. 1C is an illustration of geographical service areas in a cellularcommunication system 150 where the transition communication station 108is connected to the compensation communication station 110 through abackhaul 152. Therefore, for the example of FIG. 1C, the transitioncommunication station 108 is a separate and distinct device from thecompensation communication station 110. Such an arrangement may occur,for example, where the transition communication station 108 is amacrocell base station providing a relatively larger service area andthe compensation communication station, such as a microcell base stationor picocell base providing a relatively smaller service area. In somesituations, the various sized service areas may be implemented witharrangements similar to the example of FIG. 1B. When the communicationstation providing the larger service has adequate capacity, thecommunication station may be used for transition area management and thelarger service area may be used as the transition service area.

FIG. 2 is an illustration of a coverage transition where the energysaving service area 106 is deactivated and the compensation service area104 is expanded to provide wireless service within the geographicalregion of the energy saving service area 106. In the example of FIG. 2,a coverage area configuration transition within the system of FIG. 1C isshown progressing through five stages. In the interest of clarity andbrevity, a single UE device 118 is shown in the example.

In the first stage 202, the UE device 118 is communicating over wirelesscommunication link 204 with the communication station 112 of the energysaving service area 106. For the example, the UE device 118 is at leastreceiving control signals and may also be transmitting control signalsand exchanging data with the communication station 112 prior to thecoverage transition. The coverage transition may be initiated inresponse to a determination that the energy saving service area 106should be deactivated and the compensation service area 104 should beexpanded. Such a determination may be based on any of several factorsand circumstances where some examples include the resource load on theenergy saving service area, the compensation service area, and thecoverage service area. The resource load of a service area is based onthe amount of time and frequency resources being used by all of the UEdevices within the service area. The determination for deactivating theenergy saving service area may be based on whether the compensationservice area has the resource capacity available to provide service tothe UE devices within the ES service area and whether the transitioncommunication station 108 has the resource capacity available totemporarily provide service to the UE devices within the energy savingservice area 106. As another example, the determination for deactivatingan energy saving service area may be based on a particular time day,month, etc., where an operator has determined that the traffic load atthis time can be managed without the energy saving service area. Inresponse to the determination that the energy saving service area shouldbe deactivated, the coverage area configuration transition is initiated.

At the second stage 206, the UE device 118 is transferred to thetransition service area 102. For the example, the transfer is a handoverprocedure in accordance with an LTE communication specification. Thetransfer may also be referred to as a handoff in some circumstances. Thetransfer results in changing the serving cell of the UE device 118 fromthe energy saving service area 106 to the transition service area 102. Awireless communication link 208, therefore, is established between UEdevice 118 and the communication station 108 where control signals anddata signals can be exchanged between the transition communicationstation 108 and the UE device 118.

The third stage 210 of the transition procedure is initiated after allof the UE devices within the energy saving geographical service area aretransferred to other services areas. At this stage, the energy savingservice area 106 is deactivated. The circle representing the energysaving service area 106 is shown with a dashed line to indicate that theservice area is no longer active. As a result, the energy savingcommunication station (eNB) 112 does not provide wireless service withinthe energy saving service area by transmitting or receiving wirelesssignals. For the example herein, the energy saving communication station112 is turned off and consumes little or no power.

The fourth stage 212 of the transition procedure is initiated after allof the UE devices within the energy saving geographical service area aretransferred to other service areas and the energy saving service areahas been deactivated. At this stage, the compensation service area 104is expanded until it covers at least a portion of the geographical areapreviously serviced by the energy saving service area 106. In theexample of FIG. 2, the compensation service area 104 is expanded tocover the entire geographical area previously serviced by the energysaving service area 106. The service area 104 may be expanded using anycombination of known techniques such as increasing transmission power,antenna tilting, and using antenna beam forming techniques. Thetransition communication station 108 continues to serve the UE device118 within the transition service area 102 as the compensation servicearea is expanded.

The fifth stage 214 of the transition procedure is initiated after thecompensation service area expansion is complete. At this stage, the UEdevice 118 is transferred to compensation communication station 110. Forthe example, the transfer is a handover procedure in accordance with theLTE communication specification. The transfer may also be referred to asa handoff in some circumstances. The transfer results in changing theserving service area of the UE device 118 from the transition servicearea 102 to the compensation service area 104. A wireless communicationlink 216, therefore, is established between UE device 118 and thecompensation communication station 110 where control signals and datasignals can be exchanged between the communication station 110 and theUE device 118.

FIG. 3 includes illustrations 300, 301 of a coverage area transitionwhere the transition service area covers a plurality of smaller serviceareas and the compensation service area is expanded to cover more thanone energy saving service area. The circular shapes representing theservice areas generally illustrate the relationships between the serviceareas and do not necessarily depict the actual shapes of the serviceareas. In addition, the service areas may overlap in some regions morethan in other regions. The open areas shown between the circular shapedservice areas in the figure do not necessarily indicate that no serviceis available in these areas and are merely a product of illustrationutilizing simple shapes to represent a more complicated relationshipbetween service areas. Further, the service areas may contain holes ofcoverage where service is unavailable. In the interests of clarity andbrevity, such features are not illustrated in the figures.

For the example of FIG. 3, the transition service area 102 covers thegeographical areas of several smaller service areas 104, 106, 302, 304,306, 308, 310 including the compensation service area 104 and threeenergy saving service areas 106, 302, 304. In the transition state 300before the compensation area is expanded, the energy saving serviceareas 106, 302, 304 have coverage areas adjacent to the compensationservice area 104. In the transition state 301 after the compensationservice area is expanded, the compensation service area 104 has acoverage area that includes the original coverage area of thecompensation service area 104 and at least portions of the coverageareas of the energy saving service areas 106, 302, 304. For the example,the expanded compensation service area 312 covers the areas previouslycovered by the energy saving service areas 106, 302, 304. The expandedcompensation service area 312, therefore, is the compensation servicearea 104 with a larger coverage area. The energy saving service areasare shown with dashed lines in the coverage state 301 to illustrate thatthe service areas have been deactivated. The coverage area transitionprocedure for multiple energy saving service areas is similar to thetransition procedure for a single energy saving service area discussedabove. In one example, the compensation service area expands to covereach energy saving service area serially. In other words, thecompensation service area is expanded to cover a first energy savingservice area before a second energy service area. In such an example,all UE devices in the first energy saving service area are transferredto the transition service area, the compensation service area isexpanded to cover the first energy saving service area, and the UEdevices are transferred to the compensation service area prior to theprocedure being performed for next energy saving service area. In theexamples discussed below, however, the compensation service area isexpanded to cover multiple energy saving service area areas in a singlecoverage area transition procedure. In this example, all UE devices fromall energy saving service areas are transferred to the transitionservice area, the compensation service area is expanded, and all the UEdevices are transferred to the compensation service area. In somecircumstances, some UE devices may be transferred to neighboring smallservice areas (306, 310) instead of the transition service area.

FIG. 4 is an illustration of the service areas 102, 104, 106 withneighbor service areas. The example of FIG. 4 includes only a singleenergy service area 106. In the interest of clarity and brevity, FIG. 1,FIG. 2 and FIG. 3 illustrate only a limited number of service areas. Intypical implementations, numerous service areas cover large geographicregions. A typical system includes multiple transition service areas aswell as numerous smaller service areas. FIG. 4 shows a section ofgeographical region where several service areas provide ubiquitouscoverage. The circular shapes representing the service areas generallyillustrate the relationships between the service areas and do notnecessarily depict the actual shapes of the service areas. In addition,the service areas may overlap in some regions more than in otherregions. The open areas shown between the circular shaped service areasin the figure do not necessarily indicate that no service is availablein these areas and are merely a product of illustration utilizing simpleshapes to represent a more complicated relationship between serviceareas. Further, the service areas may contain holes of coverage whereservice is unavailable. In the interests of clarity and brevity, suchfeatures are not illustrated in the figures.

Each service area includes neighbor service areas that are adjacentservice areas or otherwise near the service area. Service areas 104,302, 304, 402, 404, 406 are neighbor service areas of the energy savingservice area 106. Since the compensation service area is the expandingservice area it is not consider a neighbor service area for theparticular coverage area transition. As a result, the neighbor serviceareas for the example discussed herein are shown with crosshatchedshading in FIG. 4. During the coverage area transition, the UE deviceswithin the energy saving service area(s) may be transferred to aneighbor service area instead of the transition service area. Forexample a UE device receiving service from the energy saving servicearea 106 but positioned sufficiently close to the neighbor service area404, may be transferred to the neighbor service area 404 during thecoverage area transition.

As discussed below, neighbor service areas are notified of the change incoverage areas after the coverage area transition. Therefore, allneighbor service areas are informed of the expansion of the compensationservice area and the deactivation of the energy saving service area whenthe transition is complete.

FIG. 5 is a message flow diagram 500 between the compensationcommunication station 110, the energy saving communication station 112and other communication stations 502. The other communication stations502 include at least the neighbor communication stations providingservice within the neighbor service areas of the energy saving servicearea 106. The other communication stations 502 are communicationstations that need to have information regarding the status of thecompensation service area and the energy saving service area. Thecommunication stations are connected through a backhaul that istypically wired but may include at least portions that are wirelesscommunication links. For the example, the communication stations areeNBs that communicate through the backhaul over an X2 link in accordancewith LTE communication standards. Other communication techniques can beused in some circumstances.

For the example shown in FIG. 5, in response to determining that theenergy service area should be deactivated, the energy savingcommunication station (ES eNB) 112 sends a Cell State Change Requestmessage 504 to the compensation communication station (compensation celleNB) 110. The Cell State Change Request message 504 at least indicatesto the compensation communication station 110 that the energy savingcommunication station is requesting change in its status from active toinactive. Unless provided by another procedure, this message may alsoinclude the energy saving service area's current load information, whichthe compensation service area may use to determine if it has thecapacity available to provide service to the UE devices within theenergy saving service area. In one example, the Cell State ChangeRequest is part of a dedicated procedure for this feature that is addedto a standard specification. In other circumstances, the Cell StateChange Request message 504 function may be incorporated into messagingstructures and procedures currently defined by a communication standard,such as the Load Management or eNB Configuration Update procedurescontained in the LTE communication standard. In either case,modifications of the LTE communication standard can facilitate theprocedure.

In response to the Cell State Change Request message 504, thecompensation communication station 110 determines whether it can expandservice to the energy saving service area. If it cannot, thecompensation communication station 110 responds with a Cell State ChangeResponse message 506 indicating that the compensation service area willnot be expanded. Otherwise, as in the example of FIG. 5, thecompensation communication station 110 responds with a Cell State ChangeResponse message 506 indicating that the compensation service area willbe expanded. In one example, the Cell State Change Response is part of adedicated procedure for this feature that is added to a standardspecification. In other circumstances, the Cell State Change Responsemessage 506 function may be incorporated into messaging structures andprocedures currently defined by a communication standard, such as theLoad Management or eNB Configuration Update procedures contained in theLTE communication standard. In either case, modifications of the LTEcommunication standard can facilitate the communication.

After receiving the confirmation that the compensation service area willbe expanded, the energy saving communication station 110 transfers allthe UE devices it is serving to the transition service area or aneighboring service area at event 508. For the examples herein, ahandover procedure in accordance with the LTE communicationspecification is used to transfer the UE devices.

When all the UE devices have been transferred from the energy savingservice area, the energy saving service area is deactivated at event510. As discussed herein, a service area is “deactivated” when it nolonger transmits downlink signals to UE devices and does not receive orprocess uplink signals from UE devices. Therefore, a deactivated servicearea cannot provide wireless service to UE devices. The communicationstation that provides the energy serving service area still includesactive functions and is not turned off. For example, the communicationstation is still capable of communicating with other communicationstations and/or the network.

After the energy saving service area is deactivated, the energy savingcommunication station sends a Cell Status Change Update message 512indicating that the service area has been deactivated and that thecompensation service area can be expanded. In one example, the CellState Change Update message 512 is part of a dedicated procedure forthis feature that is added to a standard specification. In othercircumstances, the Cell State Change Response message 512 function maybe incorporated into messaging structures and procedures currentlydefined by a communication standard, such as the Load Management or eNBConfiguration Update procedures contained in the LTE communicationstandard. In either case, modifications of the LTE communicationstandard can facilitate the communication.

At event 514, the compensation service area is expanded in response toreceiving the Cell Status Change Update message 512. The compensationcommunication station increases transmission power and performs otherknown techniques for expanding the compensation service area to cover atleast a portion of the energy saving service area service area. Forexample, techniques such as antenna tilting and antenna beam forming maybe used to provide an expanded service area of the compensationcommunication station that covers the original service area of theenergy saving service area as well as the original service area of thecompensation service area. Where multiple energy saving service areasare deactivated the compensation service area is expanded to cover thoseservice areas. In one example, the parameters for establishing theexpanded coverage area are determined at the time of equipmentdeployment. For example, signal quality measurements may be made and theparameters may be determined using the signal measurements at the timeof or after equipment installation. Accordingly, the compensationcommunication station applies stored values or values it has receivedfrom an Operations and Maintenance (OAM) system to expand the servicearea to cover the areas of the energy saving service areas that havebeen deactivated. This example showing explicit signaling messages isonly for illustration and other means can be used to trigger the statechanges for this procedure. For example, OAM system may provide signalsfor this purpose, or may provide values for the time duration of eachstate in the procedure. For example, OAM could provide the compensationcommunication station the time duration before it should begin theexpansion of the compensation service area. This time duration could bebased on the expected amount of time required for the energy savingservice area UE devices to be handed over to a transition service area.

In another example, the extent of the expansion of the compensationservice area is based on feedback provided by UE devices. The transitionservice area communication station may request that UE devices reportsignal strength measurement information about the transition servicearea in relation to the compensation service area. For example, in thecase where the expanded compensation service area covers the same areaas the transition service area, the compensation service area coverageshould be the same as the transition service area coverage. Thetransition communication station can request UE devices to measure thesignal strength of both the transition service area transmitter and thecompensation service area transmitter. The transition communicationstation can compare the two signal strength measurements and notify thecompensation communication station if the difference between themeasurements is greater than a predetermined threshold. The compensationcommunication station can expand or reduce the compensation service areabased on the difference between the measurements. If the measurementsmade by the UE devices are the same within a certain threshold, it islikely that the coverage for the two service areas is close to the same,including at the edge of the service area even if there is no UE devicelocated there to report measurements. Similarly, for cases where theservice areas are not the same, the relationship between their signalstrengths can be determined beforehand, such as during deployment, andcan be used to assist to determine when the compensation service areahas been expanded to the proper extent. In addition, communicationstations with neighboring service areas can also use measurements fromtheir UE devices to assist with this process.

After the compensation service area has been expanded, the compensationcommunication station sends a Cell State Change Update message 516indicating that the service area is expanded.

At event 518, the UE devices previously receiving service from theenergy saving service area(s) are transferred to the compensationservice area. In some situations, one or more of the UE devices may betransferred to other services areas or may remain with the transitionservice area. For the example, handover procedures in accordance withLTE specification are invoked to transfer the UE devices from thetransition service area or the neighbor service area to the compensationcommunication station that now is providing an expanded service areacovering the original service areas of the energy saving servicearea(s). The conventional handover triggering conditions in effect inthe system may be used. Since the compensation service area is closer tothese UE devices than the transition service area, many of the UEdevices previously served by the energy saving service area will behanded over to the compensation service area.

A communication station configuration update message 520 is sent fromthe energy saving communication station to the other communicationsstations indicating that the energy saving service area is no longeractive. The other communication stations include at least the neighborstations of the energy saving service area and may include othercommunication stations that require information regarding the status ofthe energy saving service area. For example, this functionality could beadded to the LTE X2 interface eNB Configuration Update message thatcommunication stations use to notify other communication stations aboutconfiguration changes of their service areas (cells).

A communication station configuration update message 522 is sent fromthe compensation communication station to the other communicationsstations indicating that the compensation service area has beenexpanded. The other communication stations include at least the neighborstations of the energy saving service area and may include othercommunication stations that require information regarding the status ofthe compensation service area. For example, this functionality could beadded to the LTE X2 interface eNB Configuration Update message thatcommunication stations use to notify other communication stations aboutconfiguration changes of their service areas.

For the example above, the order of events may be modified in somecircumstances. For example, the UE devices may be transferred to thecompensation service area after the communication stations configurationmessages 520, 522 are transmitted to the other communication stations502.

FIG. 6A is an illustration of coverage areas in a cellular communicationsystem 600 where coverage area transitions are managed using atransition cell 102 provided by a compensation communication station108. The arrangement is similar to the example discussed above where thetransition service area is provided by communication station separatefrom the compensation communication station. For the example of FIG. 6A,however, the transition service area is provided by the compensationcommunication station. The compensation communication station,therefore, provides wireless service within two geographical areasrepresented by two circular areas where one circular area is acompensation service area and the other, larger circular area is thetransition service area. The transition service area 102 overlaps withthe compensation service area 104 and an energy saving service area 106.In typical implementations of the cellular communication system 600,several adjacent transition service areas may cover large areas whereeach transition service area includes several smaller cells positionedadjacent to each other within the transition service area 102. In theinterest of brevity and clarity, however, FIG. 6A shows only two smallercells 104, 106 within a single transition service area 102. The circularshapes representing the service areas of the cells generally illustratethe relationships between the cells and do not necessarily depict theactual shapes of the service areas. The coverage area transitionmanagement techniques discussed with reference to FIG. 6A may be appliedto numerous coverage area transition scenarios. For example, severalenergy saving service areas may be deactivated and a compensationservice area may be expanded to cover the geographical service areas ofthe multiple energy saving service areas in accordance with thetechniques discussed herein. The service areas may have any of severalshapes and sizes.

Communication stations 108, 112 transmit and receive wireless signals toprovide the cells 102, 104, 106. Each communication station 108, 112,which also may be referred to as an access node, access point, eNodeB,eNB, base station, and other terms, includes a transceiver and stationcontroller. The transceiver, or radio head, is typically collocated withthe station controller although, in some situations, the stationcontroller may be physically separated from the radio head. The radiohead at least includes radio frequency (RF) transceiver equipment suchas antennas, transmitters, and receivers, for transmitting and receivingwireless signals. Typically, radio heads do not include higher levelprocessing and control functions which are performed by the associatedcontroller. The radio heads may be near a controller where both theradio head and the controller may be implemented within a singleapparatus. Also, each communication station may include more than oneradio head. As discussed below with reference to FIG. 6B, for example, asingle station controller can be connected to a transition radio headand a compensation radio head. Since the location, shape, and size ofthe cell is determined at least in part by wireless transmission andreception with the communication station, the cell's location isdetermined by the location and operation of the radio head. Thecompensation communication station 108 provides the transition servicearea 102 and the compensation service area 104 and an energy savingcommunication station 112 provides the energy saving service area 106.Each communication station 108, 112, therefore, provides wirelesscommunication services to wireless communication user equipment devices(UE devices) 114, 116, 118 within a geographical service area. Severalcommunication stations are typically interconnected through a backhaul(not shown in FIG. 6A) and to a network controller (not shown in FIG.6A) to provide several service areas to cover large areas. The backhaulmay include any combination of wired, optical, and/or wirelesscommunication channels. For the examples herein, the network controllerincludes the functionality of the Mobility Management Entity (MME) andthe Packet Gateway (P-GW).

As discussed above, a cellular communication system is typicallyrequired to adhere to a communication standard or specification. Thecellular communication system 600 for the examples of FIG. 6A and FIG.6B operate in accordance with 3GPP LTE.

Therefore, for the examples herein, the compensation communicationstation 108 includes a wireless transceiver that transmits downlinksignals 122 to one or more UE devices 114 within the transition servicearea 102 in accordance with 3GPP LTE and receives uplink signals 120from one or more UE devices 114 within the transition service area 102in accordance with 3GPP LTE. The compensation communication station 110also transmits downlink signals 124 to one or more UE devices 116 withinthe compensation service area 104 in accordance with 3GPP LTE andreceives uplink signals 126 from one or more UE devices 116 within thecompensation service area 104. The energy saving communication station112 includes a wireless transceiver that transmits downlink signals 130to one or more UE devices 118 within the energy saving service area 106in accordance with 3GPP LTE and receives uplink signals 128 from one ormore UE devices 118 within the energy saving service area 106 inaccordance with 3GPP LTE.

The compensation communication station 108 uses different frequencies toprovide the compensation service area 104 and the transition servicearea 102. For the example of FIG. 6A, a first downlink/uplink frequencypair is assigned for the transition service area 102 and a seconddownlink/uplink frequency pair is assigned for the compensation servicearea 104. Several downlink/uplink frequency pairs may be assigned toeach service area 102, 104. The first downlink frequency is differentfrom the second downlink frequency and the first uplink frequency isdifferent from the second uplink frequency. The first downlink frequencyand the first uplink frequency are not used by the energy savingcommunication station. Accordingly, communications in the transitionservice area do not interfere with communications in energy savingservice areas 106 even though the cells overlap because differentfrequencies are used. Where more than one frequency pair is used by eachservice area, no frequency pairs used by the transition service area areused by any of the energy saving service areas within the transitionservice area 102.

FIG. 6B is an illustration of the cellular communication system wherethe compensation station includes a station controller 132 and two radioheads 134, 136. As mentioned above, a communication station may includemore than one radio head. For the example of FIG. 6B, the stationcontroller 132 of the compensation communication station is connected toa transition radio head 134 and a compensation radio head 136. Thetransition radio head 134 exchanges wireless signals 120, 122 with UEdevices 114 within the transition service area 102. The transitionservice area 102 may be a cell or other service area that continuallyprovides wireless services to UE devices in accordance with knowntechniques. The transition service area may also facilitate managementof dynamic coverage area transition when the transition service areaincludes adequate capacity. The compensation radio head 136 exchangeswireless signals 124, 126 with UE devices 116 within the compensationservice area 104.

FIG. 7 is an illustration of a coverage area configuration transitionwhere the energy saving service area 106 is deactivated and thecompensation service area 104 is expanded to provide wireless servicewithin the geographical service area of the energy saving service area106. In the example of FIG. 7, a coverage transition within the systemof FIG. 6A or FIG. 6B is shown progressing through five stages. In theinterest of clarity and brevity, a single UE device 118 is shown in theexample. Also, although not shown, the compensation communicationstation 108 may include more than one radio head.

In the first stage 702, the UE device 118 is communicating over wirelesscommunication link 704 with the communication station 112 of the energysaving service area 106. For the example, the UE device 118 is at leastreceiving control signals and may also be transmitting control signalsand exchanging data with the communication station 112 prior to thecoverage transition. The coverage transition is initiated in response toa determination that the energy saving service area 106 should bedeactivated and the compensation service area 104 should be expanded.Such a determination may be based on any of several factors andcircumstances where some examples include the resource load on theenergy saving service area, the compensation service area, and thecoverage service area. The resource load of a service area is based onthe amount of time and frequency resources being used by all of the UEdevices within the service area. The determination for deactivating theenergy saving service area may be based on whether the compensationservice area has the resource capacity available to provide service tothe UE devices within the ES service area and whether the transitioncommunication station 108 has the resource capacity available totemporarily provide service to the UE devices within the energy savingservice area 106. As another example, the determination for deactivatingan energy saving service area may be based on a particular time day,month, etc., where an operator has determined that the traffic load atthis time can be managed without the energy saving service area. Inresponse to the determination that the energy saving service area shouldbe deactivated, the coverage transition is initiated.

At the second stage 706, the UE device 118 is transferred to thetransition service area 102. For the example, the transfer is a handoverprocedure in accordance with an LTE communication specification. Thetransfer may also be referred to as a handoff in some circumstances. Thetransfer results in changing the serving cell of the UE device 118 fromthe energy saving service area 106 to the transition service area 102. Awireless communication link 708, therefore, is established between UEdevice 118 and the communication station 108 where control signals anddata signals can be exchanged between the coverage communication station108 and the UE device 118. The frequencies used for the communicationlink 708 with the compensation communication station 108 are differentfrom the frequencies used for the communication link 704.

The third stage 710 of the transition procedure is initiated after allof the UE devices within the energy saving service area 106 aretransferred to other services areas. At this stage of the transitionprocedure, the energy saving service area 106 is deactivated. The circlerepresenting the energy saving service area 106 is shown with a dashedline to indicate that the service area is no longer active. As a result,the energy saving communication station (eNB) 112 does not providewireless service within the energy saving service area by transmittingor receiving wireless signals. For the example herein, the energy savingcommunication station 112 is turned off and consumes little or no power.

The fourth stage 712 of the transition procedure is initiated after allof the UE devices within the energy saving service area 106 aretransferred to other service areas and the energy saving service areahas been deactivated. At this stage, the compensation service area 104is expanded until it covers at least a portion of the geographical areapreviously serviced by the energy saving service area 106. The cell 104may be expanded using any combination of known techniques such asincreasing transmission power, antenna tilting, and using antenna beamforming techniques. The compensation communication station 108 continuesto serve the UE device 118 within the transition service area 102 usingthe communication link 708 as the compensation service area 104 isexpanded.

The fifth stage 714 of the transition procedure is initiated after thecompensation service area expansion is complete. At the fifth stage 714,the UE device 118 is transferred to the compensation service area. Thecommunication resources using the frequencies assigned to thecompensation service area 108 are scheduled to the UE device 118. Forthe example, the transfer is in accordance with the LTE communicationspecification and results in changing the serving cell of the UE device118 from the transition service area 106 to the compensation servicearea 104. Where the compensation station includes a transition radiohead and a compensation radio head, the UE device 118 is transferredfrom the transition radio head 134 to the compensation radio head 136 byscheduling the communication resources assigned to the compensationradio head. A wireless communication link 716, therefore, is establishedbetween UE device 118 and the compensation radio head 136 of thecompensation communication station 108 where control signals and datasignals can be exchanged between the compensation radio head 136 of thecommunication station 108 and the UE device 118. In situations, thefifth stage may not be performed. For example, the transition radio head134 can continue to provide service to the UE device 118 until atransfer is warranted.

The dynamic coverage area transition procedure for examples where thecompensation communication station 108 provides the transition servicearea 102 may be performed for multiple energy saving service areas.Arrangements such as those described with reference to FIG. 3,therefore, apply to the transition procedure where the transitionservice area 102 covers the geographical areas of several smallerservice areas 104, 106, 302, 304, 306, 308, 310 including thecompensation service area 104 and three energy saving service areas 106,302, 304.

The messaging between the communication stations for the dynamiccoverage area transition procedure for examples where the compensationcommunication station 108 provides the transition service area 102 issimilar to the examples discussed with reference to FIG. 5. Forarrangements where the compensation communication station 108 providesthe transition service area 102, the Cell State Change Request message504, Cell State Change Response message 506, Cell Status Change Updatemessage 512, Cell State Change Update message 516, communication stationconfiguration update message 520, and communication stationconfiguration update message 522 are formatted and transmitted asdiscussed with reference to FIG. 5. For event 518, the communicationstation may perform UE device handovers in an implementation-specificway since the target and source of the handovers are controlled by thesame communication station and no signaling between communicationstations is required.

For the example, handover procedures in accordance with LTEspecification are invoked to transfer the UE devices from the transitionservice area or a neighbor cell to the compensation communicationstation that now is providing an expanded cell covering the originalservice areas of the energy saving service area(s).

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. The above description is illustrative and not restrictive.This invention is to be limited only by the following claims, whichinclude all such embodiments and modifications when viewed inconjunction with the above specification and accompanying drawings. Thescope of the invention should, therefore, be determined not withreference to the above description, but instead should be determinedwith reference to the appended claims along with their full scope ofequivalents.

What is claimed is:
 1. A base station for controlling a first cellcomprising: a controller configured to control the first cell so thatthe first cell replaces at least part of a coverage of a second cell inresponse to modification of the coverage of the second cell; and atransmitter configured to transmit an eNB configuration message, whichindicates that the first cell replaces the at least part of the coverageof the second cell, to another base station not managing the secondcell.
 2. An apparatus provided in a base station for controlling a firstcell comprising: a controller, wherein the controller is configured toperform processing of: controlling the first cell so that the first cellreplaces at least part of a coverage of a second cell in response tomodification of the coverage of the second cell; and transmitting an eNBconfiguration message, which indicates that the first cell replaces theat least part of the coverage of the second cell, to another basestation not managing the second cell.
 3. A method comprising:controlling, at a base station, a first cell so that the first cellreplaces at least part of a coverage of a second cell in response tomodification of the coverage of the second cell; and transmitting, atthe base station, an eNB configuration message, which indicates that thefirst cell replaces the at least part of the coverage of the secondcell, to another base station not managing the second cell.